Follow up to !8505. Depends on !5988 to be merged first. Includes commits from both of these MRs.
Note how some sample times are still marked TODO for non-thinned mode, because seemingly after 5988, delta buffers no longer have pts. The corresponding samples are still assigned a bogus sample time, because `has_pts` isn't checked by `media_stream_send_sample`. This is probably something to address once/if 5988 gets merged.